Capacity of a Class of Broadcast Relay Channels

TL;DR

This paper derives new capacity bounds for a class of broadcast relay channels, unifying previous results and providing capacity for specific degraded cases, with applications in cellular network cooperation.

Contribution

It introduces generalized inner bounds for broadcast relay channels, unifies prior work, and determines capacity for semi-degraded and degraded cases, including Gaussian channels.

Findings

New inner bounds on capacity regions are derived.

Capacity is established for semi-degraded broadcast relay channels.

Capacity for the Gaussian case with degraded channels is obtained.

Abstract

Consider the broadcast relay channel (BRC) which consists of a source sending information over a two user broadcast channel in presence of two relay nodes that help the transmission to the destinations. Clearly, this network with five nodes involves all the problems encountered in relay and broadcast channels. New inner bounds on the capacity region of this class of channels are derived. These results can be seen as a generalization and hence unification of previous work in this topic. Our bounds are based on the idea of recombination of message bits and various effective coding strategies for relay and broadcast channels. Capacity result is obtained for the semi-degraded BRC-CR, where one relay channel is degraded while the other one is reversely degraded. An inner and upper bound is also presented for the degraded BRC with common relay (BRC-CR), where both the relay and broadcast channel are degraded which is the capacity for the Gaussian case. Application of these results arise in the context of opportunistic cooperation of cellular networks.